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Molecules 2009, 14, 5144-5164; doi:10.3390/molecules14125144
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Review
The Chemical Composition and Biological Properties of
Coconut (Cocos nucifera L.) Water
Jean W. H. Yong, Liya Ge, Yan Fei Ng and Swee Ngin Tan *
Natural Sciences and Science Education Academic Group, Nanyang Technological University,
1 Nanyang Walk, 637616 Singapore
* Author to whom correspondence should be addressed; E-Mail: sweengin.tan@nie.edu.sg;
Tel.: +65-6790 3810; Fax: +65-6896 9432.
Received: 3 November 2009; in revised form: 3 December 2009 / Accepted: 8 December 2009 /
Published: 9 December 2009
Abstract: Coconut water (coconut liquid endosperm), with its many applications, is one of
the world’s most versatile natural product. This refreshing beverage is consumed
worldwide as it is nutritious and beneficial for health. There is increasing scientific
evidence that supports the role of coconut water in health and medicinal applications.
Coconut water is traditionally used as a growth supplement in plant tissue
culture/micropropagation. The wide applications of coconut water can be justified by its
unique chemical composition of sugars, vitamins, minerals, amino acids and
phytohormones. This review attempts to summarise and evaluate the chemical composition
and biological properties of coconut water.
Keywords: coconut water; phytohormone; auxin; cytokinin; gibberellin; inorganic ion;
vitamin
1. Introduction
The coconut (Cocos nucifera L.) is an important fruit tree in the tropical regions and the fruit can be
made into a variety of foods and beverages (Figure 1). The edible part of the coconut fruit (coconut
meat and coconut water) is the endosperm tissue. Endosperm tissues undergo one of three main modes
of development, which are the nuclear, cellular and helobial modes [1] and the development of
coconut endosperm belongs to the nuclear mode. Initially, the endosperm is a liquid containing free
nuclei generated by a process, in which the primary endosperm nucleus undergoes several cycles of
OPEN ACCESS
Molecules 2009, 14
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division without cytokinesis (the process in which the cytoplasm of a single eukaryotic cell is divided
to form two daughter cells). Cytokinesis then occurs, progressing from the periphery towards the
center, thus forming the cellular endosperm layer. At first, the cellular endosperm is translucent and
jelly-like, but it later hardens at maturity to become white flesh (coconut meat). Unlike the endosperms
of other plants (e.g., wheat and corn), the cellularization process in a coconut fruit does not fill up the
entire embryo sac cavity, but instead leaves the cavity solution-filled. This solution is commonly
known as coconut water and it is of cytoplasmic origin [2]. Nutrients from coconut water are obtained
from the seed apoplasm (surrounding cell wall) and are transported symplasmically (through
plasmodemata, which is the connection between cytoplasms of adjacent cells) into the endosperm [3].
Figure 1. Foods and beverages made from coconut: (a) coconut milk and dried coconut
milk powder; (b) canned coconut water/juice and trimmed young coconuts.
Coconut water should not be confused with coconut milk (Figure 1a), although some studies have
used the two terms interchangeably (e.g., [4–5]). The aqueous part of the coconut endosperm is termed
coconut water (Figure 1b), whereas coconut milk, also known as “santan” in Malaysia and Indonesia,
and “gata” in the Philippines (Figure 1a), refers to the liquid products obtained by grating the solid
endosperm, with or without addition of water [6]. Coconut water is served directly as a beverage to
quench thirst (Figure 1b), while coconut milk is usually used as a food ingredient in various traditional
cooking recipes (Figure 1a). The main components of coconut milk are water (ca. 50%), fat and
protein [7], whereas coconut water contains mainly water (ca. 94%, Table 1). Unlike coconut water,
coconut milk, which is the source of coconut oil, is generally not used in plant tissue culture medium
formulations [8].
Compared to coconut water, there are only limited studies on the aqueous extract of coconut solid
endosperm (coconut meat or copra). Mariat et al. used coconut meat extract in orchid tissue culture to
study its effects on orchid seed germination [9]. Subsequently, Mauney et al. purified a growth factor
from the aqueous extract of coconut meat which was found to be very potent in promoting growth of
tissue cultured plants [10]. Another group, Shaw and Srivastava demonstrated the presence of purine-
like substances in coconut meat extract [11]. The purine-like substances were able to delay senescence
(the process of ageing in plants) in detached cereal leaves, which exhibited similar known
physiological effects of cytokinins. Zakaria et al. showed that the aqueous extract of coconut meat
exhibited anti-inflammatory and wound healing properties when tested on mice [12].
(b) (a)
Molecules 2009, 14
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Table 1. Chemical composition of coconut water [20,29–31].
Source information [20] [31] [29] [30]
Coconut type young young
green
mature
green mature mature
(autoclaved) young mature
Average Weight of Coconut (g) 206 (water) 565 393
Age of coconut 6 months 12 months
Source of coconut Deerfield Beach, FL Dominican Republic
Proximates (g/100g) (g/100g )
Water 94.99 94.18 94.45
Dry 5.01 5.82 5.55
Energy value 19 kcal (79 kJ)
Protein 0.72 0.12 0.52
Total lipid (fat) 0.2 0.07 0.15
Ash 0.39 0.87 0.47
Carbohydrate, by difference 3.71 4.76 4.41
Fiber, total dietary 1.1 ND* ND*
Sugars (mg/mL) (g/100g) (mg/mL ) (g/100g )
Total 2.61 9.16 21.68 13.87 15.20 5.23 3.42
Sucrose 9.18 0.93 9.18 8.90 10.70 0.06 0.51
Glucose 7.25 3.93 7.25 2.46 2.02 2.61 1.48
Fructose 5.25 4.30 5.25 2.51 2.48 2.55 1.43
Sugar alcohols Present a (mg/L )
Mannitol 0.8 0.80
Sorbitol 15
d 15.00
Myo-inositol 0.01 0.01
Scyllo-inositol 0.05 0.05
Molecules 2009, 14
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Table 1. Cont.
Inorganic ions (mg/100g) (mg/100g) (mg/100g ) (mg/100g )
Calcium, Ca 24 27.35 31.64
Iron, Fe 0.01 0.29 0.01 0.02 0.02
Magnesium, Mg 30 25 30 6.40 9.44
Phosphorus, P 37 20 37 4.66 12.77
Potassium, K 312 250 312 203.70 257.52
Sodium, Na 105 105 105 1.75 16.10
Zinc, Zn 0.1 0.07 0.02
Copper, Cu 0.04 0.04 0.04 0.01 0.03
Manganese, Mn 0.142 0.12 0.08
Selenium, Se 0.001
Chlorine, Cl 183 183
Sulfur, S 24 24 0.58
Aluminium, Al 0.07 0.06
Boron, B 0.05 0.08
Vitamins (mg/mL) (mg/100g ) (mg /L ) (mg /100 dm 3)
Vitamin C, total ascorbic acid 2.4 7.41 7.08
Thiamin (B1) 0.03 Trace Trace 0.01
Riboflavin (B2) 0.057 0.01 0.01 0.01
Niacin (B3) 0.08 0.64 ND* ND*
Pantothenic acid (B5) 0.52 0.043 0.52
Pyridoxine (B6) 0.032 Trace ND* ND*
Folate, total 0.03
Folic acid 0.003 0 0.003
Folate, food 0.003
Folate, Dietary Folate Equivalent
(DFE) 3 (µg_DFE)
Biotin 0.02 0.02
Nicotinic acid (Niacin) 0.64 0.64
Molecules 2009, 14
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Table 1. Cont.
Lipids (g/100g ) (g/100g )
Total 0.2 0.0733 0.1482
Fatty acids, total saturated 0.176 0.03 0.1
6:00 0.001
8:00 0.014 ND* ND*
10:00 0.011 0.0007 0.0028
12:00 0.088 0.002 0.0274
14:00 0.035 0.0023 0.019
16:00 0.017 0.0219 0.032
17:00 0.0009 0.0016
18:00 0.01 0.0039 0.0108
20:00 0.0016 0.0033
Fatty acids, total monounsaturated 0.008 0.03 0.02
16:1 undifferentiated 0 0.0011 0.0007
18:1 undifferentiated 0.008 0.0194 0.015
20:1 undifferentiated 0.0049 0.0019
22:1 undifferentiated 0.0011 0.0023
Fatty acids, total polyunsaturated 0.002 0.0128 0.0054
18:2 n-6undifferentiated 0.002 0.0114 0.0032
20:4 n-6 0.0014 0.0022
Amino acids (µg/mL) (g/100g ) (µg/mL) (mg/g defatted sample)
Alanine 312 0.037 16.40 127.30 177.10 198.00 1.13 3.88
β-Alanine 12
γ-Aminobutyric acid 820 1.90 34.60 168.80 173.20
Arginine 133 0.118 14.70 25.60 16.80 20.70 0.13 0.81
Asparagine and glutamine ca. 60
Aspartic acid 65 0.07 11.30 35.90 5.40 11.40 1.60 0.76
Asparagine 17.10 10.10 10.40 25.30
Cystine 0.97-1.17
b 0.014 0.00 0.00
Molecules 2009, 14
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Table 1. Cont.
Glutamic acid 240 0.165 9.40 70.80 78.70 104.90 3.44 3.75
Glutamine 80.00 45.40 13.40 2.00
Glycine 13.9 0.034 1.30 9.70 13.90 18.00 0.43 0.11
Homoserine 5.2 ND* ND* 5.20 8.80
Histidine Trace
a 0.017 3.50 6.30 Trace
a Trace
a 0.39 0.67
Isoleucine 18 0.028 0.26 0.27
Leucine 22 0.053 6.20 37.30 31.70 33.00 0.66 0.58
Lysine 150 0.032 4.40 21.40 22.50 13.00 4.72 3.41
Methionine 8 0.013 3.50 16.90 Trace
a Trace
a 0.22 0.21
Ornithine 22
Phenylalanine 12 0.037 ND* ND* 10.20 Trace
a 0.26 0.00
Pipecolic acid Trace a
Proline 97 0.03 4.10 31.90 21.60 12.90 0.52 0.95
Serine 111 0.037 7.30 45.30 65.80 85.00 0.64 1.06
Tyrosine 16 0.022 0.90 6.40 3.10 Trace
a 0.00 0.00
Tryptophan 39 0.008 0.00 0.00
Threonine 44 0.026 2.90 16.20 26.30 27.40 0.20 0.33
Valine 27 0.044 5.60 20.60 15.10 15.50 0.91 0.82
Dihydroxyphenylaline Present
a
Hydroxyproline Trace
a Trace a 4.10 Trace
a 8.20
Pipecolic acid Present a Trace
a
Nitrogeneous compounds µmol/mL
Ethanolamine 0.01
Ammonia Present
a
Organic acids (meq/mL) (meq/mL ) (mg /100 DM)
Tartaric 1.6 2.4
Malic 34.31 9.36 34.31 11.98 14.08 317 307
Citric 0.37 0.37 0.31 0.38 ND* 24.8
Molecules 2009, 14
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Table 1. Cont.
Acetic ND* 1.3
Pyridoline 0.39 mg/mL 0.43 0.39 0.18 0.27
Succinic 0.28 0.18
Shikimic and quinic acids, etc. 0.57
Enzymes
Acid phosphatase Present a
Catalase Present
a
Dehydrogenase Present
a
Diastase Present
a
Peroxidase Present
a
RNA polymerases Present a
Phytohormones (mg/mL) (mg/L )
Auxin 0.07 0.07
1,3- Diphenylurea 5.8
Cytokinin Present
a
Miscellaneous
Leucoanthocyanin Present
a
Phyllococosine Present
a
Chemical properties
pH
4.6 to
5.6
4.7±0.1 5.2±0.1
* ND = Non detectable; a No units given; b Units: g/100g dried protein; d Units: mg/mL; e Due to contamination.
Molecules 2009, 14
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Conversely, coconut water has been extensively studied since its introduction to the scientific
community in the 1940s. In its natural form, it is a refreshing and nutritious beverage which is widely
consumed due to its beneficial properties to health, some of which are based on cultural/traditional
beliefs [2,5–8,13–15]. It is also believed that coconut water could be used as an important alternative
for oral rehydration and even so for intravenous hydration of patients in remote regions [13]. Coconut
water may also offer protection against myocardial infarction [15]. Interestingly, a study has shown
that regular consumption of either coconut water or mauby (a liquid extracted from the bark of the
mauby tree, Colubrina arborescens), or particularly, a mixture of them, is effective in bringing about
the control of hypertension [16].
Apart from that, coconut water is widely used in the plant tissue culture industry [17–20]. The
extensive use of coconut water as a growth-promoting component in tissue culture medium
formulation can be traced back to more than half a century ago, when Overbeek et al. first introduced
coconut water as a new component of the nutrient medium for callus cultures in 1941 [17]. From a
scientific viewpoint, the addition of coconut water to the medium is rather unsatisfactory, as it
precludes the possibility for investigating the effects of individual components of the medium with any
degree of accuracy. The question of which components cause the growth stimulation arose
immediately. Besides its nutritional role, coconut water also appears to have growth regulatory
properties, e.g., cytokinin-type activity [8].
Some of the most significant and useful components in coconut water are cytokinins, which are a
class of phytohormones [21]. The first cytokinin, N6-furfuryladenine (kinetin) was isolated from an
autoclaved sample of herring sperm DNA in 1955 [22–23]. In 1963, Letham isolated trans-zeatin, the
first naturally-occurring cytokinin, from a plant source (unripe corn seeds) [24]. In addition to various
plant-related functions, it was also found that some cytokinins (e.g., kinetin and trans-zeatin) showed
significant anti-ageing, anti-carcinogenic, and anti-thrombotic effects [25–26].
Furthermore, micronutrients (nutrients needed in small quantities) such as inorganic ions and
vitamins in coconut water play a vital role in aiding the human body antioxidant system [27].
Hypermetabolism gives rise to an increased production of reactive oxygen species (or free radicals), as
a result of increased oxidative metabolism. Such increase in free radicals will cause oxidative damage
to the various components of the human cell, especially the polyunsaturated fatty acids in the cell
membrane, or to the nucleic acids in the nucleus [27]. Fortunately, living organisms have well
developed antioxidant systems to neutralize the most detrimental effects of these oxidizing species.
Micronutrients have important functions in this aspect. For example, they act directly to quench free
radicals by donating electrons, or indirectly as a part of metallo enzymes (a diverse class of enzymes
that require a catalytic metal ion for their biological activity) such as glutathione peroxidase (selenium)
or superoxide dismutase (zinc, copper) to catalyse the removal of oxidizing species [28].
Other components found in coconut water include sugars, sugar alcohols, lipids, amino acids,
nitrogenous compounds, organic acids and enzymes [20,29–31], and they play different functional
roles in plant and human systems due to their distinct chemical properties. The myriad of compounds,
both known and unknown, provide coconut water with the special biological properties that is known
to the typical layman. In this paper, we will present a summary on the chemical composition of the
known compounds in coconut water.
Molecules 2009, 14
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2. Chemical Composition of Coconut Water
2.1. Phytohormones
Phytohormones are a group of naturally occurring organic compounds that play crucial roles in
regulating plant growth in a wide range of developmental processes. Initially, the term phytohormone
was synonymous with auxin. Later on, the other plant growth regulators such as gibberellins (GAs),
ethylene, cytokinins, and abscisic acid (ABA) were categorized together with auxins as the “classical
five” hormones [21]. Coconut water contains auxin, various cytokinins, GAs and ABA (Table 2)
[4,32–35].
Table 2. Naturally-occurring phytohormones unequivocally identified in coconut water.
Source information [4] [32–34] [35]
Coconut type young green mature*
Auxin nM μg mL-1
indole-3-acetic acid
150.6 0.25 ± 0.03
0.75 ± 0.04
1.46 ± 0.13
0.71 ± 0.12
0.78 ± 0.10
Cytokinins
N6-isopentenyladenine 0.26
dihydrozeatin 0.14
trans-zeatin 0.09
kinetin 0.31
ortho-topolin 3.29
dihydrozeatin O-glucoside 46.6
trans-zeatin O-glucoside 48.7
trans-zeatin riboside 76.2
kinetin riboside 0.33
trans-zeatin riboside-5’-
monophosphate
10.2
14-O-(3-O-[β-D-galacto-
pyranosyl-(1→2) -α-D-
galactopyranosyl- (1→3) -
α-L-arabinofuranosyl]-4-O-
(α-L-arabinofuranosyl)-β-
D-galactopyranosyl)-trans-
zeatin riboside
Present
Gibberellins
gibberellin 1 16.7
gibberellin 3 37.8
Auxin
indole-3-acetic acid 150.6
Molecules 2009, 14
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Table 2. Cont.
* Five coconut water samples were analysed.
2.1.1. Auxin
Coconut water contains indole-3-acetic acid (IAA), the primary auxin in plants [34,35]. IAA is a
weak acid (pKa = 4.75) that is synthesized in the meristematic regions located at the shoot apex and
subsequently transported to the root tip in plants [36]. For many years, tryptophan was assumed to be
the precursor of IAA and this was later confirmed using experiments involving seedlings of Phaseolus
vulgaris subjected to stable isotope labeling studies [37]. IAA occurs not only in the free form, but is
also conjugated to various amino acids, peptides, or carbohydrates. These IAA conjugates are
biologically inactive and appear to be the IAA storage forms in seeds and are probably involved in
hormonal homeostasis [38].
Auxin is implicated in many regulatory processes in plants especially those relating to plant growth
and development [39–40]. Auxin functions in the relay of environmental signals such as light and
gravity, the regulation of branching processes in shoots and roots, and as discovered more recently, the
patterned differentiation of cells in meristems and immature organs [39]. Undoubtedly, it is a versatile
spatial-temporal signal. Auxin transport generates auxin concentration maxima and gradients within
tissues that are instrumental in the diverse regulation of various plant developmental processes,
including embryogenesis, organogenesis, vascular tissue formation and tropisms. The unique signal-
molecule transport mechanism of auxin to a large extent underlies the remarkable developmental
plasticity of plants that allows their growth and architecture to fit the environment changing [41].
2.1.2. Cytokinins
Cytokinins, being able to induce plant cell division, were discovered in the 1950s [22,42–43].
Natural cytokinins are N6-substituted adenine derivatives with various substituted groups, and the
physicochemical behaviour of cytokinins is a function of side chain(s), sugar, phosphate and degree of
purine ring and/or side chain modification [43]. The auxin-cytokinin hypothesis predicted that
cytokinins, together with auxins, play an essential role in plant morphogenesis by controlling the
formation of roots and shoots and moderating their relative growth [42]. Cytokinins are a class of
phytohormones that exert various roles in the different aspects of plant growth and development, e.g.,
cell division, formation and activity of shoot meristems, induction of photosynthesis gene expression,
Abscisic acid
65.5
0.010 ± 0.002
ND
0.023 ± 0.002
0.061 ± 0.019
0.071 ± 0.018
Salicylic acid
1.01 ± 0.10
0.67 ± 0.04
1.03 ± 0.12
1.79 ± 0.21
1.22 ± 0.07
Molecules 2009, 14
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leaf senescence, nutrient mobilization, seed germination, root growth and stress response [22,42–46].
Evidently, cytokinin-deficient plants generally develop stunted shoots with smaller apical meristems.
The plastochrone of these cytokinin-deficient plants is prolonged, and leaf cell production is only 3-
4% of wild type plants (with normal cytokinin metabolism), indicating an absolute role of cytokinins
in leaf growth. Cytokinins are required during leaf formation, both to drive the cell division cycle at
normal rates and to obtain the required number of divisions in order to produce a normal leaf size [42].
In addition, cytokinins are also involved in promoting the transition from undifferentiated stem cells to
differentiated tissues [47]. Unlike the growth-promoting role of cytokinins in the shoot apical
meristem, cytokinins have a negative regulatory function in root growth whereby it suppresses cell
division in plant roots [42].
Furthermore, cytokinins play an important role in retarding or even reversing leaf senescence
[44–46]. Gan and Amasino reported on the three approaches used to investigate the inhibitory role of
the cytokinins in plant senescence: the external application of cytokinins, the measurement of
endogenous cytokinin levels before and during senescence, and the manipulation of endogenous
cytokinin production in transgenic plants. However, externally applied cytokinins were not always
effective in blocking the senescence of excised leaves. The effect of cytokinins on senescence can also
vary under different experimental conditions. These studies revealed an inverse correlation between
cytokinin levels and the progression of senescence in a variety of tissues and plant species. Cytokinins
can interfere with senescence in detached tissues of dicotyledons and monocotyledons but are often
less effective in attached tissues. In addition, cytokinin levels, as well as the capacity to synthesize
cytokinin, decline with the progression of leaf senescence [48].
Coconut water is an important additive in the tissue culture media of several plants, including
orchids and traditional Chinese medicinal herbs. The cytokinins found in coconut water support cell
division, and thus promote rapid growth. They are mostly used to propagate protocorm-like bodies of
orchids in plant industries [49]. However, it should be noted that cytokinins cannot completely
substitute coconut water’s effects. This is due to the presence of other phytohormones (such as auxin
and gibberellins [33–35]) or even undefined chemical components which may exert synergistic effects
with cytokinins. One advantage of coconut water is that it results in considerable plant cell
proliferation without increasing the number of undesirable mutations [20]. Coconut water contains
various cytokinins (Table 2). For this review, only kinetin, trans-zeatin and their derivatives will be
discussed in greater detail as they are known to possess medicinal values [26,50–52].
N6-Furfuryladenine (Kinetin)
The first cytokinin, kinetin was discovered by Miller et al. in Wisconsin. It was a degradation
product of herring sperm DNA and was found to be able to promote cell division in plants [22–23].
Kinetin was previously assumed to be an unnatural and synthetic compound, until in 1996
Barciszewski et al. detected it in freshly extracted cellular DNA from human cells and in plant cell
extracts [53]. And recently, Ge et al. identified kinetin and kinetin riboside from coconut water [54].
Being one of the cytokinins, kinetin has the effects on the plant developmental processes that could
be influenced by cytokinins, such as leaf expansion and seed germination. Most importantly, kinetin is
well known for its ability to retard senescence in plants [48,55–58].
Molecules 2009, 14
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Recently, its strong anti-ageing effects on human skin cells and fruitflies (Zaprionus paravittiger)
were also reported [26,59–60]. Kinetin slowed down the ageing processes, and prolonged the lifespan
of fruitflies, which was mainly due to a reduction in age-specific death rates throughout the adult
lifespan [59]. In addition, kinetin enhanced cell division and led to fewer cells being arrested at the
G0/G1 phase, thus delaying the ageing of endothelial cells and increasing cell proliferation and
metabolic capacity [61]. Most importantly, the anti-ageing effects of kinetin did not increase the cell
culture lifespan in terms of maximum proliferative capacity in vitro, in contrast to many other anti-
ageing factors which are known to promote carcinogenesis under certain conditions [26,62]. Kinetin
was shown to delay the onset of several cellular and biochemical characteristics associated to cellular
ageing in human skin fibroblast cultures [26]. Based on the results obtained from studies on the anti-
ageing effects of kinetin on human skin cells [63], skin care products containing kinetin were
subsequently developed to treat photo-damaged skin [64].
Recent research evidence revealed that oxidative DNA damage plays an important role in cancer
development and that dietary antioxidants can provide effective protection against oxidative damage
[65]. Kinetin was shown to act as a strong antioxidant both under in vitro and in vivo conditions. A
study done by Olsen et al. demonstrated that kinetin protected DNA from oxidative damage mediated
by the Fenton reaction. Kinetin inhibited the formation of 8-oxo-2’deoxyguanosine, which is a
common marker of oxidative damage in DNA [66]. In addition, kinetin was found to inhibit oxidative
and glycoxidative protein damage generated in vitro [67]. The anti-oxidative properties of kinetin
suggested that it may also prevent the oxidative damage of unsaturated fatty acids located within the
cell membranes [68].
Kinetin riboside exhibited a cytotoxic effect on plant crown-gall cells [69]. Its anti-proliferative and
apoptogenic effects against human cancer cells were also well documented. Studies on the inhibition
of kinetin and kinetin riboside on the growth of human fibroblasts, epithelium and mammary
carcinoma were conducted [70–72]. A recent study revealed that kinetin riboside could induce
apoptosis in HeLa and mouse melanoma B16F-10 cells [50]. Moreover, kinetin riboside also has
significant effects on inhibiting the growth of human heptamoa (HepG2) cells [73]. Cabello et al. later
found that the cytotoxic effects of kinetin riboside stemmed from its ability to induce rapid ATP
depletion, creating genotoxic stress which activates p21 and other stress response genes [74].
Furthermore, a research group from the Mayo clinic (USA) identified kinetin riboside from a chemical
library screen as the suppressor of cyclin D1 and D2 (CCND1 and CCND2) expression, showing that
kinetin riboside could potentially act as a therapeutic agent for multiple myeloma [75].
Besides anti-ageing and anti-cancer effects, kinetin has effective anti-platelet properties, and may be
a potential therapeutic agent for treating arterial thrombosis. Kinetin inhibited platelet aggregation in
human platelets when stimulated by an agonist [76], and could therefore help to prevent blood clots
[77–78].
trans-Zeatin
trans-zeatin was the first naturally-occurring cytokinin identified from a plant source (Zea mays) by
Letham [24]. In 1974, Letham identified trans-zeatin in coconut water [79–80], and a year later, van
Stadens and Drewes verified the presence of both trans-zeatin and trans-zeatin riboside in coconut
water [81]. trans-zeatin riboside is the most abundant type of cytokinin found in coconut water
Molecules 2009, 14
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(Table 2). trans-zeatin is normally used to induce plantlet regeneration from callus in plant tissue
culture. Based on experimental data, trans-zeatin plays a key role in the G2-M transition of tobacco
cells. It was found to override the blockade of mitosis caused by lovastatin which inhibits cytokinin
biosynthesis and controls cellular entry in mitosis [82].
Recent studies showed that trans-zeatin can be a potential drug to treat neural diseases. Some
researchers found that trans-zeatin actually possesses an inhibitory effect on acetylcholinesterase and it
can be used to treat Alzheimer’s disease or related neural dysfunctions, such as dementia [51,52].
Acetylcholinesterase degrades the neural compounds that mediate neural transmission, and thus by
blocking its action, synaptic transmission can be improved. Another recent study also found that trans-
zeatin can prevent amyloid β-protein formation, which has a causal role in the development and
progress of Alzheimer’s disease [83]. On the other hand, like kinetin, trans-zeatin also exhibited anti-
ageing effects on human fibroblast cells [84].
2.1.3. Gibberellins (GAs)
GAs are a class of phytohormones which exert certain effects on plant growth and development, in
aspects such as seed germination, epidermal cell elongation, leaf expansion and flower development.
The main biological action of GAs is their ability to stimulate the elongation of plant shoots and
induce the growth of stems in rosette and dwarfish forms. Together with auxins, GAs stimulate
cambial activity and in effect, causing the formation of large xylem and phloem cells in woody plants
[85–87]. Apart from the vital roles played in plants, recent study also showed that gibberellin
derivatives have anti-tumor bioactivities [88]. Chemically, all known GAs are gibberellic acids (a
family of diterpenoids acids), and there are currently 136 members of GAs identified based on their
chemical structures. GAs are numbered neither by their structural information nor by their functions,
but rather in the order of their identification [85,87]. GA1 and GA3 were successfully detected and
quantified in coconut water [33,89].
2.2. Inorganic ions
Inorganic ions are required for normal cellular function, and are critical for enzyme activation, bone
formation, hemoglobin function, gene expression, and the metabolism of amino acids, lipids and
carbohydrates [90–93]. Coconut water contains a variety of inorganic ions (Table 1) [20,29–31] and
these ions contribute to the therapeutic value inherent in coconut water. As the basic ion composition
of coconut water can replenish the electrolytes of the human body excreted through sweat, such as
sodium, potassium, magnesium and calcium, it can serve as an effective rehydration drink [94]. The
concentration of these electrolytes in coconut water generates an osmotic pressure similar to that
observed in blood [95], and it also does not affect hemostasis (plasma coagulation) [14]. As a result,
coconut water can be used as a short term intravenous hydration fluid under certain emergency
situations [13]. Interestingly, Anurag and Rajamohan showed that coconut water has cardioprotective
effects in experimental myocardial infarction induced in rats and this was probably attributed to the
rich content of mineral ions in coconut water, especially potassium [15].
Molecules 2009, 14
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2.3. Vitamins
Vitamins, which are essential for the normal functioning of the human body, are also found in
coconut water. Greater consumption of fruits and vegetables is associated with the reduced risk of
cardiovascular disease, stroke, and cancers of the mouth, pharynx, esophagus, lungs, stomach, and
colon [96–99], because they contain vitamins and minerals vital for normal physiological functions
[86]. Coconut water contains vitamins B1, B2, B3, B5, B6, B7 and B9 (Table 1). The B vitamins are
water-soluble and are required as coenzymes for enzymatic reactions essential for cellular
function [100].
Vitamin B6 (which includes pyridoxal, pyridoxine and pyridoxamine) serves as a coenzyme in
various enzymatic reactions, such as the transamination and decarboxylation reactions [101]. For
example, it is the coenzyme of γ-cystathionase [102], which catalyses the cleavage of cystathionine,
releasing α-ketobutyrate and cystein [103]. The α-ketobutyrate molecule is subsequently converted
into succinyl-CoA and fed to the tricarboxylic acid (TCA) cycle while cystein is involved in protein
and gluthathione biosynthesis [104–105]. Vitamin B6 deficiency can affect various processes of the
body, such as inflammation and renal function [100].
Coconut water contains folate (Table 1), also known as vitamin B9. It was identified in the late
1930’s as the nutrient required to reduce anemia during pregnancy [106]. It can prevent mitochondrial
toxicity induced by methanol metabolites. In addition, the active form of folate, 5-methyltetrahydro-
folate is believed to be one of the central methyl donors required for mitochondrial protein and nucleic
acid synthesis [28]. Lower blood levels of vitamin B6 and folate can increase the risk for
atherosclerosis and other vascular diseases [107]. Another study found that high plasma levels of
vitamin B6 and folate may reduce the risk for breast cancer [108]. In addition to vitamin B, coconut
water also contains vitamin C (total ascorbic acid, Table 1), which is an important dietary
antioxidant [28,63].
3. Conclusions
Coconut water, being a refreshing beverage, provides important health benefits. The chemical
components which contribute to its bioactivity are essential to the plant industry, biotechnology and
biomedical fields. Undoubtedly, cytokinins are currently the most important components in coconut
water. Significant advances were made in understanding the biological functions of the various
cytokinins in both plant and human systems. The potential anti-cancer properties of specific cytokinins
could bring encouraging and novel perspectives in finding cures for the different types of cancers. The
recent discovery of other medicinal values of coconut water signifies a good potential in improving
human health. Better insights and understanding of the functions and properties of the individual
components of coconut water will, therefore, help us to better utilise this marvellous and multi-
dimensional liquid with special biological properties from nature.
4. Future Studies
The chemical composition of coconut water is affected by several factors. Jackson et al. showed
that coconut water of different coconut varieties contains different concentration of compounds, and
Molecules 2009, 14
5158
that the chemical contents also varied during the different stages of maturity [109]. Soil and
environmental conditions also affect the chemical profile of coconut water. A study which was done in
Brazil demonstrated that the physical properties of coconut water were affected by varying nitrogen
and potassium application [110]. Hence, future studies should be carried out to determine the factors
that produce the desirable chemical composition for a specific purpose. Breeding studies can also be
carried out to produce coconut water enriched with specific chemical compounds.
Although coconut water is already well studied in terms of its chemical content, there may still be
unknown solutes which contribute to its special biological effects. With the development of more
advanced detection techniques, screening can be intensified to detect novel compounds of medicinal
values present in coconut water.
Acknowledgements
We would like to thank Stuart Letham (Australian National University) for sharing with us his idea
in Canberra that there are a lot of “good biochemicals and especially cytokinins” in coconut water and
that we will discover potentially novel biochemicals in these marvellous tropical fruits especially with
the technological advancement in analytical tools.
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